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The Great Sphinx looms over the Egyptian desert, keeping silent watch over the tombs of the ancient Pharaohs. A human-headed lion carved from solid limestone, the Sphinx stretches for 240 feet and rises 66 feet above its base on the far-eastern edge of the Giza Plateau, facing the Nile River and the rising sun. For decades, Egyptologists have confidently dated the Sphinx to about 2500 B.C., when the Pharaoh Khafre, also known as Chephren, allegedly commissioned its construction. But new evidence challenges that long-held theory: Examining the great statue from a geological point of view rather than an Egyptological one suggests that much of it was built around 5000 B.C. - thousands of years earlier than previously thought.
Over the years, Egyptologists have held widely diverse opinions about the age of the Sphinx. At various points in their careers, such eminent scholars of the last century as Sir Flinders Petrie, Sir E. A. Wallis Budge, and Sir G. C. Maspero considered the Sphinx older than the pyramids it guards, as did the Egyptians themselves from about 1500 B.C (the beginning of the period known as the New Kingdom) through Roman times. To this day, the villagers who live near Giza have an oral tradition that the Sphinx, which they call Abul Al-Hol, or "the Father of Terrors," is some 5,000 years older than the nearby Great Pyramid of Khufu. also called Cheops, and the smaller pyramids of Khafre and Menkaure (Mycerinus).
In recent years, the prime proponent of an older Sphinx has been John Anthony West, a writer, tour guide, and "independent Egyptologist" who has no formal degrees, credentials, or academic affiliations in Egyptology. He first came across the idea in the works of the late Orientalist, philosopher, and controversial Egyptologist R. A. Schwaller de Lubicz. Buried deep in one of his texts, Schwaller mentioned that the Sphinx showed geological weathering features that indicated it could be much older than most modern Egyptologists believed. But West has no training in geology and so could not convincingly pursue the subject on his own.
I first met West through a rhetoric professor at Boston University, where I am a science professor specializing in geology; I hold bachelor's, master's, and doctoral degrees in geology. The professor, Robert Eddy, had known West for many years and was well aware of West's ideas about the Sphinx's age. West asked Eddy to find an "open-minded" geologist to help explore his theory and Eddy designated me as a potential candidate.
When I encountered West in the fall of 1989, I found his ideas concerning the Sphinx's age a bit outlandish, but interesting. At that time, West thought the Sphinx might have been built before the Sahara became a desert - the Giza Plateau sits on the eastern edge of the Sahara, just west of Cairo - dating back to at least 10,000 B.C. He based this hypothesis on the severe weathering and erosion evident on the Sphinx's body but not on other nearby manmade structures.
West mumbled something about getting me over to Egypt to evaluate the evidence firsthand, but I figured he wouldn't fly me over there just to point out what was surely a simple error on his part. By June of 1990, though, West and I were indeed in Egypt, walking around the Giza Plateau. While I couldn't render a judgment after a week of simple observation, I became convinced that either the rocks were behaving in very strange ways or West was actually onto something.
The most persuasive piece of evidence for an older Sphinx that I found on that first trip involves the two-stage construction of the temples in front of the Sphinx. Rather than resting majestically on the top of the rocky plateau, as most people envision it, the Sphinx actually sits in a hollow - known as the Sphinx enclosure - formed when the ancient Egyptians carved away the limestone rock to shape its body. Large blocks of this limestone were used to construct two temples, and the Egyptians later covered the limestone with granite facing stones called ashlars. My field observations led me to conclude that the limestone was exposed to the elements and underwent considerable weathering and erosion before the granite was laid over it. In places, the workers cut the backs of the ashlars in an undulating pattern to complement the irregular surface - characteristic of weathering - of the limestone blocks from the Sphinx enclosure. Also, where the granite has fallen away, it's evident that the limestone beneath was not cut smoothly. Rather it shows a higgledy-piggledy surface pattern where apparently the ancient Egyptians, before resurfacing it with granite, attempted to cut back and even out the weathered surface, but didn't take off enough to make the wall perfectly smooth.
Egyptologists generally attribute the granite ashlars on the temples to Khafre: Carved into them are Old Kingdom inscriptions dating back to about 2500 B.C. It seems reasonable to assume that the limestone blocks would have been freshly cut - that is, their surfaces would have been unweathered - when initially used to construct the temples. But if the granite facing covers deeply weathered limestone, then the temples' core structures - which came from the Sphinx ditch - must predate the granite facing by a considerable degree. Since the granite ashlars date to Khafre's reign, the temples must have been erected earlier, meaning the Great Sphinx must also have been built prior to the reign of Khafre.
On my first trip to Egypt, I could only play tourist. I didn't have official permission to carry out scientific research on the Giza Plateau, and I couldn't enter the Sphinx enclosure. Upon my return to the United States, I spent several months drafting a lengthy proposal to the Egyptian Antiquities Organization (EAO), which oversees all research on the Sphinx and other monuments. I requested permission to carry out detailed, noninvasive geological studies of the rocks comprising the Sphinx and its adjacent structures, specifically looking at the stratigraphy (rock layers), weathering, erosion, and geomorphology (land forms). My studies didn't require collecting any samples, or breaking or disturbing any rocks.
In addition, I needed to examine the structure and weathering features beneath the rocks' surface and to find out what lay under piles of sand. But how could I see through 50 or more feet of sand? How could I probe nondestructively through rock to see how deeply it has weathered or whether it contains cavities, voids, or chambers? West and I ultimately decided to ask permission to pursue limited seismic investigations near the Sphinx, which the EAO granted along with the rest of our proposal.
West and I carried out the seismic work as well as other research when we returned to Egypt in April 1991. We were accompanied by Thomas L. Dobecki, a geophysicist with the Houston firm of McBride-Ratcliff, who had signed on to supervise the technical aspects of gathering and analyzing the geophysical data. The seismic research required hitting a steel plate with a sledge-hammer to generate energy waves (essentially sound waves) that traveled below the surface of the rock and sand, reflecting off of whatever was underneath. Electronic geophones - micro-phones, more or less - picked up the resulting vibrations at the surface. The geophones fed their data into a sophisticated portable seismograph, which stored it on computer disks. From the seismic data, we reconstructed cross sections of the area beneath the rock and sand, creating pictures of what lay hidden underneath our feet without disturbing more than a few pebbles.
After collecting our data, we discussed our work with colleagues at Cairo University and returned to the United States to analyze the data. I returned to Egypt in June 1991 to collect more data and further check the information I'd already gathered.
Based on the data, I've concluded that the Sphinx was built in stages. The Egyptians carved the core of the Sphinx - the front and sides - first, in at least 5000 B.C. and perhaps earlier. Later, possibly in Khafre's time, workers chiseled out the rear of the Sphinx and recarved the head. No one knows what the original head looked like: many observers consider the current head too small for the body, and it shows signs of more recent cut marks than does the body Furthermore, it has long been suggested that the face of the Sphinx portrays Khafre, but this assumption has recently been questioned: After detailed analysis, Frank Domingo, a senior forensic officer of the New York City Police Department, concluded that the face of the Great Sphinx does not match the face seen on statues of Khafre. Most Egyptologists agree that since Khafre's time, the Sphinx has been restored and refurbished many times, as evidenced by the layers of stone veneer covering much of the Sphinx's body and paws.
Geologists can date land forms by analyzing their weathering and erosion patterns. In examining the rocks of the Giza Plateau, including those incorporated into the Sphinx and nearby structures. I observed several distinct modes of weathering in identical rocks from the same formation of limestone. The Sphinx's body and the walls of the Sphinx enclosure exhibit mostly precipitation-induced weathering, giving a rolling, undulating, very deeply weathered profile to the vertical rock surface. By contrast, structures unambiguously attributed to early and middle Old Kingdom times (2600 B.c-2300 B.C.), the same time the Sphinx was supposedly built, display primarily wind-induced weathering and fairly little precipitation-induced erosion. Weathering produced by the effects of the wind looks much different from that caused by precipitation: On these structures, much of the original surface remains intact, often with hieroglyphic inscriptions still legible, but in places, the rock is softer and has consequently been worn away by wind and sand abrasion, creating gaps in the vertical rock surface.
The precipitation-induced weathering evident on the Sphinx - clearly pre-served under the oldest repairs to the statue's core, which date back to at least 1400 B.C. - harks back to an earlier, moister period of time preceding the current arid regime that has held sway on the Giza Plateau since middle and late Old Kingdom times. Both historical and geological data indicate that the area underwent a moist period, with sporadic heavy rains, between 5000 B.C. and 3000 B.C. Since then, the Giza area has simply not experienced the precipitation necessary to produce the erosional features found on the Sphinx's core body. For corroborative evidence, one need look no farther than the Saqqara Plateau, about ten miles from the Giza Plateau, where fragile mastabas, or tombs, built around 2800 B c of sun-dried mudbricks show no evidence of the precipitation-induced weathering seen on the Sphinx. Therefore, the Sphinx must predate these structures - by a considerable degree, given the depth of weathering seen in the Sphinx enclosure.
A few geologists have previously noticed the anomalous and very ancient weathering on the Sphinx's core body, but none seem to have drawn the conclusion that the Sphinx must be older than its traditional attribution of 2500 BC. In fact, the well-known geologist Farouk EI-Baz has suggested that the Great Sphinx is nothing more than a yardang - a natural erosional land form, essentially a wind-shaped hill - that the Old Kingdom Egyptians merely "dressed up" to look like a Sphinx. But EI-Baz's yardang hypothesis is untenable, because in order to carve the Sphinx's body, the ancient Egyptians had to dig a ditch around it - the Sphinx enclosure, which is clearly artificial and manmade. Moreover, substantial evidence indicates that the Egyptians used the blocks removed from the Sphinx ditch to build the temples in front of the monument.
Seismic investigations conducted on the floor of the Sphinx enclosure suggest that on the north, south, and east sides (the Sphinx faces due east), the rock has undergone considerable weathering; from the surface to a depth of between six and eight feet, atmospheric moisture has made the rock more porous and caused some mineralogical changes. Along the back or west end, the identical limestone has weathered to a depth of only about four feet - compatible with a date of about 2500 B.C. If the Egyptians had carved the entire body of the Sphinx out of natural bedrock at one time, the limestone surrounding it should show the same depth of subsurface weathering everywhere. The data we collected indicates that initially only the sides and front of the Sphinx were carved free of the rock, while what would later become the back or rump originally merged with the natural rock. If the back end dates back to about 2500 B.C. and the other three sides exhibit about 50-percent to 100-percent more weathering, then they are probably at least that much older than 2500 B.C., dating the Sphinx's core body to about 5000 B.C. The seismic data is corroborated by the precipitation-induced weathering patterns evident on the Sphinx's body and the Sphinx enclosure.
In October, I presented my Sphinx work at the Annual Meeting of the Geological Society of America in San Diego. Geologists tend to be an honest lot, and I knew that someone would surely point out any major misinterpretation of the data. Much to my relief, no one found any errors in my work. In fact, many colleagues, intrigued by the research. suggested that I call on them if they could be of assistance.
My research on the Sphinx contin-ues. Dobecki and I hope to gather more subsurface geological and geophysical data. and I plan to continue my stratigraphic. weathering, and geomorphologic studies in the Giza Plateau area. 1f the EAO permits, I'd like to collect a few very small samples of rocks from the plateau tor certain mineralogical studies that could shed more light on weathering rates and regimes. More importantly, I'd like to pursue isotopic studies of such rocks that might accurately date the initial carving of the Sphinx. This procedure measures the concentration of isotopes produced in situ on the rock surface by the bombardment of cosmic rays - high-energy particles from outer space, like protons and neutrons, that constantly bombard the atmosphere. As these particles collide and interact with atoms on a rock surface, they produce numerous new isotopes, and in some cases, the accumulation of these isotopes reveals when a rock surtace was initially exposed or, in this case, carved.
Finally, I hope to search Egypt for the remains of other major structuros buili back in 5000 B.C. by the same enterprising Egyptians who constructed the marvelous, enduring Sphinx. I predict that we will find them buried under the notorious Egyptian sands and Nile silts. The concept of an older Sphinx could herald the beginning of an exciting new era in the study of ancient Egypt